The spent fuel pool is seen from the operation room inside the No. 3 reactor building at Tepco Fukushima Dai-ni nuclear power plant in Tomioka Town.

Source: Japan National Press Club Pool

Treated water from Tokyo Electric Power Co. Holdings Inc.’s wrecked Fukushima nuclear plant north of Tokyo is safe to be released under controlled circumstances into the nearby Pacific Ocean, an independent adviser to the utility said.

“It is much better to do a controlled release in my view than to have an accidental release,” Dale Klein, the adviser and a former chairman of the U.S. Nuclear Regulatory Commission, said in an interview in Tokyo. “I get nervous about just storing all that water when you have about a thousand tanks. You have all the piping, all the valves, everything that can break. ”

More than five years after the meltdowns at Fukushima, Tokyo-based Tepco continues to struggle to contain the radiation-contaminated water that inundates the plant.

About 300 metric tons of water -- partly from the nearby hills -- flow into Fukushima’s reactor building daily, mixing with melted fuel and becoming tainted, according to the company’s website. For perspective, that’s roughly the amount of water contained in one lane of an Olympic-sized swimming pool.

The water is currently pumped out of the buildings and purified, lowering its radioactive content with a system called Advanced Liquid Processing System, or ALPS. The treated water, which still contains a radioactive element known as tritium, is then stored in one of roughly 1,000 tanks at the site.

Water Challenges

Dale Klein.

Photographer: Akio Kon/Bloomberg

What to do with the treated water remains a headache for Tepco. The utility was urged by the International Atomic Energy Agency in May 2015 to consider discharging the water into the ocean. In early 2014, Klein, the Tepco adviser, criticized the company’s progress in managing the water situation, saying at the time that the task distracted Tepco from other important challenges associated with the cleanup.

Tepco will cooperate with the government, local authorities, and fishermen regarding what to do with the tritium water, spokesman Tatsuhiro Yamagishi said by phone. As of July 28, Tepco stored 668,352 tons of treated water at the Fukushima plant, while 188,462 tons of untreated water was waiting in a second set of tanks to be processed by ALPS, according to Tepco’s Yamagishi.

The government agency overseeing handling of the treated water hasn’t decided whether to go ahead with an ocean release because it needs to “weigh any potential impact on society,” according to an official who asked to not be named, citing internal policy.

“I hope the government will help move towards a decision,” Klein said.

Nuclear power plants routinely and safely release dilute concentrations of tritiated water, according to the the U.S. Nuclear Regulatory Commission.

Release of the “water will not be a safety issue, but it will be an emotional issue,” Klein said. “A lot of people are not going to know what tritium is and they’re just going to perceive that the water is glowing in the dark.”